Mineral oil composition



' conditions. "due sensitivity to moisture and air and other on. cosmos Herschel o. Sth, Walllngfordx, mm, L. Cantrell, Lsnsdowne, Pa, assignors to Gult Oil Corporation, Pittsburgh, Pa, a corporation of Penney! No Drag. Application September 27-, 1943,

Serial No. 504,056 a .7 Claims. (Q. 252-360 This invention relates to lubricating oil compositions. More particularly, the invention is concerned with mineral lubricating oil composi tions of a character adapted'to protect ferrous and other metal surfaces to which they are applied, from rusting and other types of corrosion ifn addition to affording lubrication of such suraces.

Simple mineral oil films aficrd only a limite protection to metal surfaces from rust and other types of corrosion, but do not afford any great protection under severe conditions of use. Many so-called anti-rust lubricating oils have been proposed, consisting of mineral oils and added constituents intended to protect metallic surfaces from rust, tarnish or corrosion. Most of them are of rather limited applicability, in that'while they afiord satisfactory protection to one class of metals, they may be ineffective, or even deleterious, with another class of metals. These shortcomings of such mineral oils and oil compositions are serious inmany cases, particularly in cases wherein a plurality of metals must be simultaneously lubricated while ex to corrosive conditions; for example, in the case of copper alloy bearings with steel shafting and the case of electric motors where surfaces of both steel and copper ar exposed to corrosive Moreover, many such oils show unsubstances to which they are exposed, and lubrieating films of such oils do notefiectively propounded oils which are efiective as regards preventing rust, are deficient in lubricating prop erties.

' Among the objects of the present invention is the provision of an anti-corrosion lubricating oil composition, of good lubricating properties,

of itself free from tendency to corrode copper and other metallic surfaces, and being in itself relatively inert and unail'ected by air and mois ture.

These and other objects of the invention are achieved by the provision 01' a mineral oiicor'nform tightly adherent oil films on the metal, protecting the metal surfaces from moisture an air.

In addition, the improved oil composition itself maintaining the improved oil composition on the adapted to protect steel from rusting while being position including, as a rust inhibitor, the substantially neutral reaction products obtained by reacting di-cyclohexyl amine with acid phosphate esters oi alkylated phenols containing at leastproximately equimolecular proportions undersuch conditions that the reaction product or mixture has a pH value between 5.5 and 7.5.

We have found that such improved oil compositions are very effective as anti-corrosion lubricants for metal surfaces in general. They surfaces thereof remain bright indefinitely and copper alloy bearings (which present a difiicult problem in protection from corrosion) are maintained in their highly finished condition even under unfavorable conditions of use. Further, copper, aluminum, zinc, tin, silver, and their alloys are all effectively guared against corrosion and are well lubricated by these improved oil compositions containing our new rust inhibitors.

In general, various improved lubricants, such as household lubricants, machine oils, gun oils, turbine oils, slushing oils and the like are prepared, by selecting a suitable lubricating oil or base and dissolving the required amount of the above described reaction products in the oils.

In particular, the invention finds special utility in preparing improved oil compositions of the so-called household type, useful for lubricating light mechanisms such as electric motors, guns, etc. and containing relatively light (low viscosity) oils as the lubricating base. That is, the invention is especially well suited for improving highly refined lubricating oils having a Saybolt Universal viscosity ranging from 60 to 150 at F.; mineral oils of 100 viscosity being especially suitable for preparing our improved oil compositions.

In general, from 0.01 to 25.0 per cent of the inhibitor is suflicient to impart to, lubricating oils adequate rust-inhibiting properties. More concentrated oily solutions or oil mixtures of the inhibitor can be prepared, as a stock solution or concentrate, which can be diluted with lubricating oil to form a rust-preventive lubricant. Usually 0.5 per cent or less of the inhibitor is suf fi cient'to impart to mineral lubricating oil adequate rust-inhibiting roperties for metal articles exposed to moisture and air, but as much as 25 per cent by weight on the oil is sometimes incor-" porated to afiord prolonged and complete protection fromrust under extremely severe conditions. Such highly concentrated compositions still retain excellent lubricating and other characteristics in addition to affording practically complete rust protection under extraordinary conditions.

The reaction products we employ are relatively stable compositions under ordinary conditions. At room temperatures some of them are heavy viscous oily liquids, while others are soft solids which melt to oily liquids at slightly elevated temperatures. All of them are relatively non-volatile. They are insoluble in water and more or less water repellent. They are very re- These advantageous rust inhibitors can be readily prepared from di-cyclohexyl amine and acid phosphate esters of alkylated phenols containing at least one branched chain alkyl group, by reacting said amine and acid-phosphate esters together in approximately equimolecular proportions, as stated ante. In preparing our rust inhibitors or reaction products, the reaction is con-- trolled so as to produce substantially neutral reaction products or mixtures having a pH'value between 5.5 and 7.5 (as measured with quinhydrone-calomel electrode assembly) The di-cyclohexyl amine, employed as one re actant, is a well known chemical compound: it being a secondary amine having the following formula:

F This secondary amine, as a C. P. chemical, is a colorless liquid having a boiling point of 254-6 C.

cycloh'exyl amine salts thereof present purposes.

The other reactant, the acid phosphate esters are di-esters of ortho-phosphoric acid and may be represented by the following generic formula:

R R V l I? I n I n wherein R, R and R" represent hydrogen or an alkyl group, at least one branched chain alkyl group being present. The acid phosphate diestersof trl-alkylated phenols containing a plurality of branched chain alkylgroups, such as tertiary and secondary butylgroups, are especially advantageous in the practice of this invention, particularly those in which R is a tertiary butyl group and R and R" are alkyl groups selected from the class consisting of methyl, secondary butyl and tertiary butyl groups, as more fully shown post.

It readily reacts with acid phosphate esters and other acid compounds, forming addition products therewith: these addition products being substituted ammonium salts of the acid employed. Further, this amine is soluble in mineral oils. Accordingly, in preparing our rust inhibitors, the

di-cyclohexyl amine may be reacted with the said acid phosphate esters in situ in the mineral oil as described post. Again. as also shown post, our rust inhibitors may be prepared by directly reacting the said acid phosphate esters with dicyclohexyl amine.

In either method of preparing our rust inhibitors, a C. P. ,di-cyclohexyl amine may be employed with advantage: but this is not essential in the commercial practice of this invention. For nstance, di-cyclohexyl amine is also commercially available as a technical chemical; these technical grades of di-cyclohexyl amine being a substantially pure di-cyclohexyl amine and containing only traces of other amines. usually monoand tri-cyclohexyl amines as impurities. For example, one of the commerc al grades ad vantageous for the present purposes has the following properties:

This technical material has a specific gravityoi 0.9104 (ZS/25 C.) andis substantially pure'di- Other technical or commercyclohexyl amine. cial grades of-di-cyclohexyl amine may also be employed in making our rust inhibitors. In seneral, the commercial di-cyclohexyl amines readily react with the acid phosphate esters forming di- These acid phosphate esters can be prepared by various methods from alkylated phenols containing one or more branched chain alkyl groups attached .to the phenyl nucleus in the positions indicated ante.

In particular, the acid phosphate iii-esters of -4-tertiary-butyl phenol, 2-tertiary-butyl-4-secondary butyl, 2:4-di-tertiary-butyl-phenol, 2:6- di-tertiary butyl 4 secondary butyl phenol, 2 4: B-tfl-tertiary-butyl phenol, 2 e-di-tertiarybutyl i-methyl phenol, and 4:6-di-tertiary-butylz-methyl phenol are advantageous for the present purposes. For instance, as shown in the illustrated examples post, di-(2,4,6-tri-tertiary-butyl phenyl) phosphate having the formula H1O 0m mc-c-om" lilzG-l-CH:

are advantageous in preparing our rust inhibitors.

These two acid phosphate'di-esters areviscous oily liquids at room temperature and are readily soluble in mineral oils. Accordingly, mineral all solutions of these acid phosphate'esters may be employed in preparing concentrates of our rust inhibitorsin oil; the amine being added to such all solutions and reactedwith the acid phosphate esters dissolved therein to form the rust inhibitor in situ in the oil. In general, acid phosphate diesters of alkylated phenol containing tertiary or secondary alkyl groups are useful and advantageous in preparing our rust inhibitors; those containing a plurality of such; branched chain albl groups being particularly advantageous for the present purposes. Such acid phosphate di-esters are readily soluble in mineral oils and have other properties rendering them advantageous for the purposes of this invention.

suitable for the As a class, these acid phosphate (ii-esters of alkylated phenols containing branched chain alkyl groups react readily with di-cyclohexyl amine. In general, the reaction is exothermic and is quite vigorous in most cases. In preparing our rust inhibitors, the reaction temperature is controlled by suitable means to secure smooth reaction and obtain addition products of the amine and acid phosphate ester. In doing so, the temperature of the reaction mixture is controlled by cooling or heating as required; the temperature of the reaction mixture being maintained below 180 F. to avoid splitting out water from the mixture. The reaction temperature is usually maintained between 140 and 170 F. during the larger portion of the reaction and within this range excellent rust inhibitors are obtained; the pH value of the reaction product being adjusted in the final stages of the reaction within the desired range stated ante.

The following examples illustrate advantageous methods of preparing these rust inhibitors:

Example I.-To a suitable kettle equipped with heating and cooling coils and means for mechanical agitation, there were added 181 pounds of commercial di-cyclohexyl amine and then 586 pounds of di-(2,4,6-tri-tertiary-butyl-phenyl) phosphate were slowly added, the said acid phosphate being gradually added at such rate as to keep the temperature of the reaction mixture below 180 F. whereby to avoid splitting out water from the mixture. After the addition of the acid phosphate, the mixture had a pH of 4.1 and was brought to the desired pH of '73 by adding 14.0 pounds of di-cyclohexyl amine and stirring the final mixture for one hour.

The substantially neutral reaction product so obtained is a heavy viscous oily liquid when cooled to room temperature. This reaction-product or rust inhibitor was light amber red in color and had a pleasant odor. It was sufiiciently soluble in mineral oils for the present purposes.

Similar viscous oily rust inhibitors can be readily obtained having other pH valueswithin the range of 5.5 to 7.5, by controlled adjustment of the pH during the last stages of the reaction.

Likewise, our oily rust inhibitors also can be prepared from other primary fatty amines and other acid phosphate diesters and alkylated phenols as well as from the particular amines and acid phosphate employed in Example I. The preparation of other such advantageous rust inhibitors is illustrated in the following example.

Example lI.-Here again, the reaction is carried out in a suitable kett e equipped with means for heating and cooling and for agitating the mixture.

Into such a kettle there were introduced 181 pounds of commercial di-cyclohexyl amine and then 474 pounds of di-(2,4-di-tertiary-butylphenyl) phosphate were gradually added with stirring. The reaction was vigorous and quite exothermic and the acid phosphate was added at such a gradual rate as to facilitate maintaining the reaction temperature below 180 F., the reaction being cooled if desired to maintain it below that temperature. In this way, the reaction temperature was maintained between 140 and 170 F. during the larger portion of the reaction. After all the acid phosphate had been added, the mixture was warmed to facilitate completion of the reaction. At this stage the reaction mixture had a pH between 3 and 4 and the final adjustment had a pH of.6.1.

and.control of the pH value was then effected.

were added and the mixture further heated with stirring until 'the reaction product had a pH of approximately 6.8.

The rust inhibitor so obtained was a heavy viscous oily liquid when cooled to room temperature and was sufilciently solublein mineral oils for making our improved'compositions.

In other words, the substantially neutral reaction products obtainedin Examples I and II, respectively, like the amine and acid phosphate esters from which they were prepared, are soluble in mineral oil. Accordingly, we sometimes prepare concentrated solutions of these rust inhibitors in mineral oils by forming them in situ in the oil. In such processes, the amine is first dissolved in the mineraloil and then the acid phosphate ester added. the mixture being stirred and maintained at the desired temperature until the reaction is complete, and the mixture has a pH value within the specified range. In preparing such oil concentrates of our rust, inhibitors sometimes an additional amine is added in the later stages to adjust the pH value as desired. The concentrates or oil solutions of neutral reaction products so obtained are useful addition agents to various types of lubricants. The prepwith means for heating and cooling and agitation. The initial temperature of the oil was 80 F. To this oil were added 181 pounds of di-cyclohexyl amine, whichwas thoroughly mixed with the oil by mechanical agitation and the final temperature of this mixture was 82 F. To the oilamine mixture, 586 pounds of di-(2,4,6-tri-tertlary-butyl-phenyl) phosphate were added over a period of two hours, during which time the mixture was agitated and the temperature of the reaction mixture rose to 178 F. After stirring for one hour, the pH of the mixture was 4.8. In order to increase this value to the desired range, 6.0 pounds of di-cyclohexyl amine were added to the mixture and stirred and the resultant mixture To secure a final adjustment, 7.0 additional pounds of di-cyclohexyl amine were added to the mixture which after stirring for one hour and cooling to room temperature had a pH of 7.4. The oily mixture prepared in this Example can be regarded as a sort of concentrated solution which can be stored indefinitely and incorporated in lubricating oils as desired to prepare commercial anti-rust oils and improved lubricants.

In general, the rust inhibitors or reaction products prepared as described ante, may be dissolved in various types of mineral oils and improved anti-rust and non-corrosive oil compositions obtained which are capable of inhibitingor retarding the rusting of various metals as described. The preparation of such improved mineral oil compositions is illustrated in the following examples:

Example IV.--A household-type lubricant was prepared by dissolving 0.1' per cent by weight of the rust inhibitor obtained in Example I in a refined oil. t L.

Example V.Another household-type lubricant was prepared by dissolving 0.1 per cent by weightof the rust inhibitor obtained in Example II in a refined oil.

The properties of theimproved oil compositions I 1 1 of Examples iv and Vante as compared with the 1 1 i propertiesof thebase oil employed are as follows:

1 Theseimproved oil compositions have excellent lubricating properties: They also effectively pm- I 1 test steel and other metals against rusting and- -corrosion.---m-. 1 w 1- 1 Infacathe improved oil: compositions ofExf 1 1 amples 11V and I V, when tested for non-rusting. gpropertiesby the various acceleratedcorrosion '1 tests' described post; :save' excellent results 381- 1'eompared .witnthebase oil. For; instance, in ;:special corrosion test No. l; the base oil began 1 toshowrustona steel strip after'sixzhonrs in 1 1 the test; whereas after twelve days the improved 1.01 showed; no evidence oi. rust. 1 Intheother and Improved lubricant i 1 i water and at the end of l2 days the-water=layer 1 1 1 1 1 is removed by Syphon andifresh water is added.= i 1 1 1 the metal surface ispreferentiallywettedbythe 1 'oilgthat is, unless the oil: him is} capable of spreading :on the metal: surface and displacing 1 water therefrom. 1

for: the protective propertiesof oils and oil come Inother words, this .test israther a drastic'one 1 1 ,1 positions asregardsthe prevention-of rust,=tarnishand corrosionrzForinstanoe inthistest yordinarily. a steel strip shows rust in about 1 :61 hours and a copperjstrip-will tarnish within approximately l2hoursiwhen an uninhibited oil- -is.so tested. on the other hand,-generally the- I 1 additionof as little as 0.1 percent by weight of more. drastic corrosion test described post, I these 1 1 1 i improved oils: showed :even greater superiority 1 I 1 1 over :thebase oil as retards protecting :steel and other metals against tarnish andcorrosionr 1 The 1 1 1 i results of these special corrosion tests are sum- 1 i -1 ;'marized in thefollowingtable; 1a j 1 1\Improvedlubricamm 1specialcorrosioniestfl"Bsseoil =i =1:"t i i '-I :TI-EX-IV I-EX.iV"-

Steel shine.. Peasant; Passes. Copper sin-in. I ic-1---,-.- 1 Do. 1 1

Steel strip Fails Passes"..- Passes. Copper strip -do .-.do Do.

Steel strip Fails Passes... Passes. Copper strip do do Do.

The special corrosion tests referred to in the above table were as follows:

Test No. 1.--36 cc. of the oil or oil composition to be tested and 4 cc. of distilled water are put in a 1" by 6" Pyrex test tube and a polished strip of copper or steel is immersed in the liquids. To mix the oil and water 2000 cc. of air per hour are bubbled through the mixture from a point within the bottom of the test tube. The apparatus is set in a water bath maintained at 122 F. (50 C.) and the original water level in the tube is maintained by additions of fresh water over 2-1 hours. The test is continued for twelve days regardless of whether or not the metal strip showed signs of corrosion. This test may also be carried out with other metal strips such as zinc, silver and tin as well as with copper or steel strips.

In this test, the lower part-of the metal strip is completely immersed in the water and the only way the oil can wet the metal surface is for the oil to creep down over it against the water pressure. Accordingly, rusting immediately begins at the level where the oil and the water meet, unless our rustinhibitors to the-oil will maintain both A copper-fiend steel strips freefrom tarnish and rust 1 1 1 1 i TestNo. 2.--In this test, its cc. urine oilor perwds sta maximumduration- I I 'oi"iihistest. 1

oil composition'to'be tested and 20 cc. of distilled I 1 i 1 waterare placed in a 400 cc; beaker ,:anda pol-- l 1 1 1 1 ished metal: strip is immersed in the cit-water r i I 4 mixture; 2000 cc. of. humidified air per hour were. I 1 E i 1 1 passed through the mixtureandthe apparatus is 1 1 i 1 maintainedat 122:F. as in Test-No.:l. The water 1 1 1 level is maintained bydaily additions oidistilled 1 I 1 1 l 1 The water removed is analyzed determine 1 I 1 whether the inhibitor; is being extracted or 1 1 leached from the oil solution; Fresh strips are. added whenthe water is changedgso as1'toprei 1 I 1 1 sent afresh metalsurf ace to the partially leached 1 1 1 1 I i toil This cycle is continued for 72 days "unless I 1 1 the test specimen becomes too corroded,; making further testing impractical. In this'test; the test 1 1 i 1 1 1 specimens are usually steel, copper, tin and zinc;

' 1 although other special metals may be used. I 1 1 1 1 Test N0. Zip-The apparatus outlined in Test =1:1No.-11isemployed and the testmgconditionsare.

identical, except that water containing: sodium 1- f f chloride in the: concentration equivalent to that '1' of thetotal salt content of sea water is added in- 1 stead of distilled water. This is a much more severe test and is conducted also for 12 days, the water level being'maintained in the same manner as for Text No. 1.

In general, the s ial corrosion tests described ante are drastic tests of the rust-preventive properties of oil compositions. In these tests, the strip 1 01' steel or other metal is subjected to attack by moisture, and air under extremely severe condition particularly in Test No. 3. Further, the oil film on the metal and the oil itself are exposed to not only the leaching action of the water but also to oxidation. Accordingly, if rusting is prevented undoisuch drastic conditions in these tests, there is good-assurance that the inhibitor will be capable of preventing. or at least retarding rusting even under extremely severe service conditions. Therefore, an inhibitor which when dissolved in an 011 permits the oil to pass all three of these tests, is com-idered an excellent inhibitor.

As shown ante, improved oil compositions containing our rust inhibitors have successfully passed all of these tests. Further our improved oil composition in addition to having excellent antirust properties are also excellent lubricants. Likewise. as shown ante, the anti-rust properties of the improved oil may be controlled by selecting the rust inhibitor and varying the proportions thereof incorporated in the oil. For instance, in certain special cases, where the prevailing conditions are so extreme as to require the lubricant to be extremely highlyprotective toward metal surfaces, a higher percentage of rust inhibitor is intained in Example I was incorporated in a sultable oil base. The oil base selected and the improved lubricant made from it have the followin properties:

weight of our-compounds is added to a used motor oil. Adding the highly potent rust preventive compound during the latter part of the break-in period for the new engine, with operation for sufilcient time after addition to assure full mixing and coating of parts, will prevent rusting.

Extensive tests in which the pH values of the agent of the presentinvention as employed in lit Base oil Improved oll Gravity API 28.5 28.4 Viscosity, sUv,1co 110 109 Color, N PA 1.25 1. 25

This improved oil is capable of preventingrusting and corrosion of metals'under extreme con- I ditions, even in the presence of salt and salt water. For instance, when tested by the special corrosion test Nos. 1 and 3 ante, the improvedoil showed no evidence of corroding either copper or steel after 12 days in either of the above tests. On the other hand, the base oil allowed the steel strip to rust in approximately 8 hours in the fresh water (Test No. 1) and in about 3 hours in the salt water test (Test No. 3). Also, with the base oil, the copper strips were coated with a greenish deposit after overnight testing: the copper strips being more slowly attacked than the steel strips but nevertheless substantially tarnished and corroded.

The specific embodiments described above are merely illustrative of the practice of this invention and other embodiments thereof may be used as desired; for instance, these rust inhibitors are compatible with various other compounding ingredients and they may be added to blended oil bases or compounded lubricants to obtain other types of improved lubricants. Improved oil compositions can be prepared from base oils containing varying amounts of fatty oils admixed with mineral oil, such blends being especially useful as household lubricants. By the present inventon, any of the previously known household or other lubricants containing relatively light lubricatin oils can be improved by adding small amounts of our rust inhibitors as described.

The invention is equally applicable to heavy mineral oils, petrolatum oils, greases, and jellies; in fact to any petroleum lubricant or coating oil,

dill

(lit

in which corrosion-preventive properties are desired. In the claims the term petroleum lubricantincludes mineral oils, jellies and the like even when used for purposes other than strict lubrication; e. g., slushing oils and gun greases.

One important application of the present invention is to the prevention of rusting in automotive and aviation engines before or after these have been used, either upon aging in intermittent actual service or in storage of engines or planes awaiting completion of assembly, shipment, and other delays after engine break-in. Such rusting is aggravated by the presence in the crankcase and crankcase-oil of moisture, sulfur, oxidation products from petroleum, tetraethyl lead, decom-.

finished oils were varied, confirm our discovery that the optimum results for a given amount of the agent in oil are secured when the pH value is maintained within the stated range of 5.5 to 7.5 for the compounding agent. There is usually a slight drop in pH value in the dilute finished oil solution as compared with the values for the compounding agents or mixtures thereof. The finished oil (which usually contains only a small proportion of the dilute compounding agent) should test between 5.0 and 6.0; advantageously around 5.7.

Any substantial departure from the stated range either on thealkaline or acid side gives less desirable results. For example, with an unduly low pH value (acid side) there is some rusting of steel surfaces by our steelptrip corrosion test, while compositions with an excessively high pH value (alkaline side) may produce greenish corrosion effects on the corrosion tests with copper surfaces and the like, although not afiecting steel to any appreciable extent. The exact adjustment is attained in preparing the rust inhibitor compound by reacting the desired molecular proportions of the two agents in the manner described.

and after the neutralization or compounding reaction has progressed practically to completion, testing the reaction product, and making any minor adjustments that are necessary for exact control by adding the required small additional proportion of the amines (if on the acid side of our desired range) or of the acid phosphate ester (if on the alkaline side). In measuring the pH of the anti-rust agents of the present invention and oils containing them, which are both substantially water-insoluble, the sample is dissolved in normal butanol (which contains a small amount of water) adjusted exactly to pH 7.0. The butanol acts as a blending agent for the water and the relatively insoluble material, but does not appreciably alter the pI-i value as it is of pH exactly 7 itself. Measurement is made by electrometric or colorimetric procedures; the re- 7 suits agree closely.

What we claim is: v

1. improved oil composition, eflective as a lubricant for metal surfaces and capable of preventing corroslon thereof in the presence of moisture and air, comprising a petroleum lubricant containing in solution therein a small proportion of the substantially neutral addition products of di-cyclohexyl amine and acid phosphate di-esters of tri-alkiylated phenols having the following formula a wherein R. represents a tertiary'butyl group and R and nlre'present an alml group selected from the class consisting of methyl, secondary butyl and tertiary butyl groups, said substantially neutral addition products having a pH between 5.5 I

and 7.5 and the prop rtion thereof dissolved in the lubricant being sumcient to prevent rusting of ferrous metals.

2. The improved oil compodtion of claim 1 wherein said substantially neutral addition product is an addition product 01' di-cyclohexyl amine and di-(2,4,6-tri-tertiary-butyl-phenyD phosphate having a pH value of 7.2.

wherein it represents a m i w butyl group and R and'R." represent an allrvi group selected asvnaca from the class consisting of methyl, secondary butyl and tertiary butyl groups, said substantially neutral addition product having a pH between 5.5 and 7.5 and theprcportion thereof being sumcient to prevent rusting of ferrous metals.

5. The improved oil composition of claim 5 wherein mineral lubricating oil is a light mineral oil having a Saybolt Universal viscosity between and 150 seconds at F.

6. The improved oil composition of claim 5 wherein said substantially neutral addition product is an addition product of di-cyclohexyl amine and di-(2,4,6-tri-tertiary-butyl-phenyl) phos-' phate having a pH value of 7.2.

7. An improved lubricating oil for metal surfaces, capable of preventing corrosion thereof in the presence of moisture and air, comprising a light mineral oil of viscosity between 60 and seconds SUV at 100 F. containing between 0.01 and 10.0 per cent of a substantially neutral addition product of di-cyclohexyl amine and di-(2,4,6- tri-tertiary-butyl-phenyl) phosphate, said addition product having a pH value of 7.2, and the proportion thereof being sumcient to prevent rusting of ferrous metals.

HERSCHEL G. SMITH. TROY L. CANTRELL.

CERTIFICATE OF CORRECTION.

Patent No. 2,571,853

HERSCHEL G. SMITH, ET .41..

March 20 191 It is hereby certified that error appears. in the printed specification of the aboye numbered 'patent requiring correction as followsz Page 5 first column, line 1 .9, for diesters and" read --d1esters of--; page, second column, lines '6 and 10 respectively, for the claim reference numeral 5" read -l the Patent Office.

and that the said Letters Patent should be,re ad with this correction therein that the same may conform to the record of the case in Signed and sealed this 12th day of June, -A., D, 1915.

' (Seal) Leslie Frazer Acting Commissionerof iat'ents. 

